Optical Inspection Apparatus and Optical Inspection Method

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2025-045700, filed Mar. 19, 2025, the entire contents of all of which are incorporated herein by reference.

Embodiments described herein relate generally to an optical inspection apparatus and an optical inspection method.

Non-contact inspection of objects is important in various industries. For example, there is a method in which a color (wavelength spectrum) of a light beam dispersed using a diffraction grating or a wavelength filter is made to correspond to a light beam direction on a one-to-one basis, and a fine structure (minute defect) on an object surface or in the object is inspected.

Hereinafter, each embodiment will be described with reference to the drawings. The drawings are schematic or conceptual, and a relationship between a thickness and a width of each portion, a ratio of sizes between portions, and the like are not necessarily the same as actual ones. In addition, even in the case of representing the same portion, dimensions and ratios may be represented differently from each other depending on the drawings. In the present specification and each drawing, the same elements as those described above with respect to the previously described drawings are denoted by the same reference numerals, and the detailed description thereof is appropriately omitted.

It is an object of an embodiment is to provide an optical inspection apparatus and an optical inspection method capable of inspecting a fine structure (minute defect) of an object surface without dispersing light from an illumination portion (light source).

According to the embodiment, an optical inspection apparatus includes: an illumination portion configured to emit illumination light including at least telecentric illumination; and an imaging portion configured to simultaneously capture telecentric light and entocentric light.

In the present specification, light is a type of electromagnetic wave, and includes gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, radio waves, and the like. In the present embodiment, light is visible light, and for example, the wavelength is in a region of 400 nm to 700 nm. It is assumed that the infrared ray has a wavelength in a region of about 700 nm to about 1 mm including near-infrared, mid-infrared, and far-infrared. The ultraviolet ray including the extreme ultraviolet ray has a wavelength in a region of about 10 nm to 400 nm.

10 1 4 FIGS.to Hereinafter, an optical inspection apparatusaccording to the present embodiment will be described with reference to.

1 FIG. 2 FIG. 2 FIG. 3 FIG. 4 FIG. 10 12 14 26 1 is a schematic cross-sectional view of the optical inspection apparatusaccording to the present embodiment.is a schematic cross-sectional view illustrating a relationship between an object S to be inspected and an imaging portion.also illustrates a light flux of an illumination light incident on the object S.is a schematic cross-sectional view illustrating a relationship between the object S to be inspected and an illumination portion.is a schematic view of a composite openingin a plane orthogonal to an imaging optical axis C.

1 FIG. 10 12 14 As illustrated in, the optical inspection apparatusaccording to the present embodiment includes the imaging portionthat images reflected light L from the object S, and the illumination portionthat irradiates the object S with an illumination light flux (illumination light beam flux) IL.

1 3 FIGS.to In the present embodiment, the object S to be inspected illustrated inmay transmit or reflect light. Alternatively, the object S to be inspected may be translucent. A point on a surface of the object S or inside the object S is referred to as an object point. Hereinafter, unless otherwise specified, it is assumed that the object S is reflective and the object point is on a surface of the object S. The surface of the object S may be referred to as an object surface or an object plane.

1 FIG. 3 FIG. 2 FIG. 2 14 1 12 16 16 12 14 16 As illustrated in, an illumination optical axis Cof the illumination portion(see) and an imaging optical axis Cof the imaging portion(see) are caused to coincide with each other using a beam splitter. Such an illumination system is referred to as coaxial epi-illumination. If the object S is transparent, it is not necessary to use the beam splitter, and the object S may be disposed so as to be sandwiched between the imaging portionand the illumination portion. The beam splittermay be a polarized beam splitter or a non-polarized beam splitter.

12 12 22 24 26 2 FIG. The imaging portionillustrated incan image telecentric light and entocentric light at the same time. The imaging portionincludes an image forming optical element, an image sensor, and a composite opening.

22 22 22 22 1 22 1 1 The image forming optical elementcan form an image of light. The image forming optical elementmay be, for example, a single lens, a set lens including a plurality of lenses, a concave mirror, a Fresnel lens, a Fresnel zone plate, a metalens, a diffraction grating, a gradient index lens (GRIN lens), or the like. That is, the image forming optical elementmay be any element as long as light can be imaged. A surface on which a set of points at infinity is imaged by the image forming optical elementis defined as a focal plane. The focal plane and its vicinity are referred to as a focal plane region. The optical axis (imaging optical axis) Cof the image forming optical elementis a straight line orthogonal to the focal plane. It is assumed that light emitted from a sufficiently distant point on the optical axis Cis imaged at a point where the optical axis Cand the focal plane intersect. This point is referred to as a focal point.

22 22 22 The image forming optical elementhas a main surface geometrically determined. A distance defined by the focal plane of the image forming optical elementand the main surface closest thereto is defined as a focal length of the image forming optical element.

22 12 22 56 14 The image forming optical element, the focal point, the focal plane, and the focal length in the imaging portionare defined as the image forming optical elementfor imaging, the imaging focal point, the imaging focal plane, and the imaging focal length, respectively. On the other hand, an image forming optical element, a focal point, a focal plane, and a focal length in the illumination portion, which will be described later, are defined as an image forming optical element for illumination, an illumination focal point, an illumination focal plane, and an illumination focal length, respectively.

12 14 The focal plane is also referred to as a Fourier plane. The Fourier plane in the imaging portionis defined as an imaging Fourier plane. A Fourier plane in the illumination portionis defined as an illumination Fourier plane.

22 22 1 22 2 FIG. 2 FIG. It is assumed that the image forming optical elementfor imaging of the present embodiment is a set lens including a plurality of lenses. Here, this is referred to as an imaging lens. However, in, for the sake of simplicity, the image forming lens which is a set lens is schematically drawn by one lens. Furthermore, the image forming optical elementfor imaging is not limited thereto, and may be any element as long as it forms an image of light. In the cross-sectional view of, the imaging optical axis Cof the image forming optical elementfor imaging is included in the present cross-section.

24 24 24 24 24 The image sensormay be a line sensor or an area sensor. However, the image sensoris not limited thereto, and any image sensor may be used as long as the image sensor has pixels capable of receiving light and converting the light into a signal. The image sensormay be a color image sensor or a monochrome image sensor. Alternatively, the image sensormay be a polarization image sensor. In the present embodiment, each pixel of the image sensorcan receive light of a first wavelength and convert the light into a signal.

2 4 FIGS.and 4 FIG. 26 32 34 26 32 34 26 36 32 34 36 32 34 36 34 36 As illustrated in, the composite openinghas a first opening regionand a second opening region. That is, the composite openinghas at least two opening regionsand. In the present embodiment, the composite openingfurther has a third opening region. The opening regions,, andmay have any shape, and may be rotationally symmetric as illustrated inor may have a stripe shape. In the present embodiment, the first opening region, the second opening region, and the third opening regionare defined by concentric boundaries. Therefore, the second opening regionand the third opening regionare considered to be the same opening region in the present embodiment.

26 22 32 34 The composite openingis disposed on or near the imaging Fourier plane (imaging focal plane) of the image forming optical elementfor imaging. The first opening regionand the second opening regionchange (modify) the properties of the light incident thereon and then pass the light, or pass the light as is without changing (modifying) the properties. Here, the optical properties are a direction, a wavelength, a wavelength spectrum, polarization, luminance, illuminance, and a light flux (light amount) of the incident light beam.

26 32 34 In the present embodiment, it is assumed that the composite openingis made of, for example, a glass plate, and the first opening regionand the second opening regionpass light of a first wavelength.

26 38 38 38 32 34 26 38 32 34 38 38 38 38 38 The composite openingmay include a shielding region. However, the shielding regionis not necessarily provided. In the present embodiment, the shielding regionis arranged so as to be connected to each of the first opening regionand the second opening region. In the present embodiment, the composite openinghas a shielding regionthat shields light having a first wavelength, which is disposed between the first opening regionand the second opening region. The first light enters the shielding region, and then the light is shielded by reflection or absorption. The shielding regionmay be formed on the glass surface by, for example, chromium vapor deposition. However, the present embodiment is not limited thereto, and the shielding regionmay be any member as long as it shields light. The shielding regionmay strongly reflect light, but it is desirable that the reflected light becomes stray light and does not become noise at the time of imaging. Therefore, it is desirable to take measures such as providing an inclination in a shape of the shielding regionto return the reflected light in a direction in which the reflected light does not become stray light.

32 26 1 32 1 34 1 34 1 32 34 32 24 34 24 32 34 32 34 34 32 24 The first opening regionin the composite openingintersects with the imaging optical axis C. That is, first opening regionincludes the imaging optical axis C. On the other hand, the second opening regiondoes not intersect with the imaging optical axis C. That is, the second opening regiondoes not include the imaging optical axis C. Therefore, the first opening regionand the second opening regionhave different optical properties. Although details will be described later, the light reflected from an object point of the object S and passing through the first opening regionis substantially telecentric light. Then, such light is received by the image sensor, whereby a telecentric image can be acquired. On the other hand, the light reflected from the object point of the object S and passing through the second opening regionbecomes substantially the entocentric light. Then, such light is received by the image sensor, whereby an entocentric image can be acquired. The entocentric light may include light that has passed through the first opening regionas well as the second opening region. In other words, an entocentric image can acquired by the light (reflected light) that has passed through both the first opening regionand the second opening region. However, in order to acquire the entocentric image, it is always necessary to acquire a light reception signal including light passing through the second opening regionby the image sensor. On the other hand, in order to acquire a telecentric image, it is always necessary to acquire a light reception signal of only light passing through the first opening regionby the image sensor.

14 1 1 1 3 FIG. 1 FIG. The illumination portionillustrated inemits illumination light IL (see) including telecentric illumination. Here, the telecentric illumination is a substantially parallel light flux along the imaging optical axis C. This is referred to as a first light flux IL. Alternatively, it is also referred to as a first incident light flux IL. The telecentric illumination includes a first wavelength. The first wavelength is, for example, 375 nm. However, the first wavelength is not limited thereto, and any first wavelength may be used. In the present embodiment, light of the first wavelength is generated by using an ultraviolet LED as a light source.

14 1 14 52 54 56 3 FIG. The illumination portionmay be any member that can emit illumination light including telecentric illumination formed by the first light flux IL. As an example for realizing telecentric illumination, the illumination portionof the present embodiment includes a projector, a light diffusion portion, and an image forming optical elementfor illumination as illustrated in.

52 52 52 52 The projectorcan form an image in the air or form an image on an object by using light from a light source in the projector. That is, the projectorcan project an image in the air or the like. There are various types of projectors. The methods mainly used include digital light processing (DLP), liquid crystal display (LCD), and liquid crystal on silicon (LCoS).

The DLP projector is a technology using a large number of minute mirrors arranged on a chip called a digital micromirror device (DMD). Each mirror on the DMD chip changes an angle at which light is reflected by voltage control to form an image. In a case where the light source is white light, light from the light source is transmitted through a color wheel in the order of red, green, and blue, and is switched at high speed, so that a full-color video can be generated. Meanwhile, there is also a three-chip DLP projector using light sources of a plurality of colors and a plurality of DMD chips.

The LCD projector is a system in which light from a white light source is divided into three primary colors of red, green, and blue, and each of the three primary colors is passed through a transmissive liquid crystal panel to form a video. A voltage is applied to each pixel of each liquid crystal panel, and brightness is expressed by adjusting a light transmission amount. The transmitted light is synthesized by a prism and projected on a screen.

The LCoS projector uses a reflective liquid crystal technology having both features of LCD and DLP. Light is controlled using a liquid crystal instead of a DMD mirror while having a reflection type mechanism like DLP. The liquid crystal panel on the silicon substrate is irradiated with light, and transmittance of each pixel is adjusted to form a video. The light source is not limited to the LED, and may be a laser. Alternatively, a conventional lamp light source, for example, an incandescent lamp or a halogen lamp may be used.

14 58 52 54 54 14 54 56 54 54 54 58 56 1 1 1 2 a a The illumination portionforms a first light emission regionon the illumination focal plane by the projector. The light diffusion portionis disposed on the illumination focal plane, but the light diffusion portionis not necessarily required. However, in a case where the illumination portionincludes the light diffusion portion, light reaches the entire surface or a wider range of the image forming optical elementfor illumination, and there is an advantage that illuminance unevenness or the like of the illumination light can be uniformized. The light diffusion portionmay be frost glass that diffuses and transmits light, or may be a holographic diffuser. However, the light diffusion portionis not limited thereto, and the light diffusion portionmay be anything as long as it diffuses light. The light passing through the first light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, the first light flux ILor the first incident light flux ILis formed at a first object point Pand a second object point P.

58 58 a. In the present embodiment, the illumination openingis defined as a space region including the first light emission region

14 56 2 56 58 2 58 1 a a The illumination portionincludes an image forming optical elementfor illumination having an illumination optical axis C. The illumination Fourier plane of the image forming optical elementfor illumination has the first light emission regionincluding the illumination optical axis C. The first light emission regionforms telecentric illumination with a first light flux ILby emitting light of a first wavelength.

10 Next, the operation of the optical inspection apparatusaccording to the present embodiment will be described.

1 1 2 It is assumed that a surface of the object S has a smooth surface orthogonal to the imaging optical axis C. This is defined as an object surface. The first object point Pis a plane. However, it is assumed that a minute defect D exists at the second object point P. The minute defect D has irregularities in which a height difference fluctuates, and a height difference thereof is typically several 10 μm or less. However, the minute defect D is not limited to this, and may be any defect as long as the height difference fluctuates.

14 1 1 2 1 2 52 56 By the illumination portion, telecentric illumination (telecentric light) formed from the first light flux ILhaving the first wavelength is incident on the first object point Pand the second object point Palong the imaging optical axis Cor the illumination optical axis C. That is, the projectorprojects an image toward the illumination Fourier plane of the image forming optical elementfor illumination to form illumination including at least telecentric illumination.

1 1 1 1 1 11 11 32 26 1 24 22 12 1 Since the first object point Pis a plane, the light flux ILincident on the first object point Pis reflected such that the incident angle and the reflection angle are equal according to the law of specular reflection. Therefore, the light of the first wavelength from the first object point Pis reflected along the imaging optical axis C. This is referred to as a first-first light beam group L. Then, the first-first light beam group Lpasses through the first opening regionof the composite openingand is imaged at a first image point Ion the image sensorby the image forming optical elementfor imaging of the imaging portion. Thus, the first object point Pconfigures a telecentric image.

2 1 2 21 21 32 34 22 12 2 24 32 34 2 On the other hand, the second object point Phas the minute defect D, and the light incident thereon is scattered and reflected in various directions as scattered light. In particular, assuming that the object S is reflective, a scattering angle distribution can be expressed by bidirectional reflectance direction function (BRDF). If the information on the scattering angle distribution is obtained, the information on the minute irregularities on the object surface can be obtained. For example, the scattering angle distribution in which light is specularly reflected on a flat object surface is narrowed. On the other hand, if minute irregularities are present on the object surface, the scattering angle distribution is generally wide. That is, scattered light in which the BRDF spreads is generated, and there is a component reflected obliquely with respect to the imaging optical axis C. The reflected light of the first wavelength from the second object point Pis defined as a second-first light beam group L. The second-first light beam group Lreaches not only the first opening regionbut also the second opening regionon the imaging Fourier plane (imaging focal plane) by the image forming optical elementfor imaging of the imaging portion. Then, an image is formed at a second image point Ion the image sensorthrough the opening regionsand. As a result, the second object point Pconfigures an entocentric image.

10 The entocentric image is formed by a light beam group having a numerical aperture (NA) larger than that of the telecentric image. The numerical aperture is an important factor for determining the resolution of the optical system, and as the numerical aperture is larger, finer details can be captured. This is because, as the numerical aperture is simply larger, a brighter and clearer image can be acquired. Another reason is that a wave-like behavior of light influences the image. A point spread function (PSF) is used to quantitatively express the influence. The PSF depends on the numerical aperture and the wavelength of light, and is expressed as an airy disk in an ideal diffraction limit. The central portion of the airy disc is the brightest, and the diffraction ring spreads around the central portion. The diameter of the minimum diffraction spot can be made smaller as the numerical aperture increases. That is, the larger the numerical aperture, the smaller the imaging spot, and the smaller the blur of the image to be acquired. Therefore, as the numerical aperture is increased, the resolution of the image is improved. As described above, by the optical inspection apparatusaccording to the present embodiment, the minute defect D becomes an entocentric image, and the plane becomes a telecentric image. Therefore, there is an effect that the resolution of the minute defect D is improved as compared with the periphery thereof and the image is clearly captured.

On the other hand, the magnification of the telecentric image becomes constant even if the position of the object S moves back and forth, and parallax and distortion do not occur. This has an effect of enabling precise dimension measurement of the object S. Further, there is an advantage that an image with uniform resolution can be acquired over the entire imaging field of view. That is, the resolution around the minute defect D can always be smaller than the resolution of the minute defect D. Therefore, there is an effect that the minute defect D can be clarified.

10 As described above, there is an effect that the optical inspection apparatusaccording to the present embodiment can sharpen the minute defect D using only the light of the first wavelength.

10 14 12 The optical inspection apparatusaccording to the present embodiment includes an illumination portioncapable of emitting illumination light including at least telecentric illumination, and an imaging portioncapable of simultaneously imaging telecentric light and entocentric light.

10 14 Therefore, according to the present embodiment, there is provided the optical inspection apparatuscapable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

14 1 12 22 1 26 22 26 32 1 34 32 34 11 21 The illumination portionforms telecentric illumination with a first light flux ILincluding light of a first wavelength, and the imaging portionincludes an image forming optical elementfor imaging having an imaging optical axis Cand a composite openingarranged on an imaging Fourier plane of the image forming optical elementfor imaging. The composite openingincludes at least a first opening regionincluding the imaging optical axis Cand a second opening regiondifferent from the first opening region. The first opening regionand the second opening regionpass light Land light Lhaving the first wavelength, respectively.

10 Therefore, for example, the optical inspection apparatusacquires the minute defect D on the object S as an entocentric image, and acquires a plane on the object S as a telecentric image. Therefore, there is an effect that the resolution of the minute defect D is improved as compared with the periphery thereof and the image is clearly captured.

In addition, the optical inspection method according to the present embodiment includes illuminating an object with illumination light including telecentric illumination, and simultaneously imaging telecentric light of reflected light from the object and entocentric light.

14 Therefore, according to the present embodiment, there is provided an optical inspection method capable of inspecting a fine structure (minute defect) of an object surface without dispersing light from the illumination portion (light source).

1 32 22 1 32 1 34 1 32 32 In the optical inspection method, illuminating the object S includes forming the telecentric illumination with a first light flux ILincluding light of a first wavelength, and the capturing includes imaging telecentric light of the reflected light through a first opening regionarranged on an imaging Fourier plane of an image forming optical elementfor imaging having an imaging optical axis C, the first opening regionincluding the imaging optical axis Cand passing the first wavelength, and capturing the image of the entocentric light of the reflected light through both a second opening regionincluding no imaging optical axis Cdifferent from the first opening regionand passing the first wavelength and the first opening region.

For this reason, for example, the minute defect D acquired by such an optical inspection method becomes an entocentric image, and the plane becomes a telecentric image. Therefore, there is an effect that the resolution of the minute defect D is improved as compared with the periphery thereof and the image is clearly captured.

10 14 Therefore, according to the present embodiment, there are provided the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

5 7 FIGS.to 10 Next, a second embodiment will be described with reference to. The present embodiment is a modification of the optical inspection apparatusof the first embodiment, and the same members as those described in the first embodiment or members having the same functions are denoted by the same reference numerals as much as possible, and a detailed description thereof will be omitted.

5 FIG. 5 FIG. 5 FIG. 6 FIG. 7 FIG. 12 10 12 14 26 1 12 10 58 2 14 is a schematic cross-sectional view illustrating a relationship between an imaging portionof an optical inspection apparatusand an object S to be inspected according to the present embodiment.is a schematic cross-sectional view illustrating a relationship with the imaging portion.also illustrates a light flux of the illumination light incident on the object S.is a schematic cross-sectional view illustrating a relationship between the object S to be inspected and an illumination portion.is a schematic view illustrating a composite openingin a plane orthogonal to an imaging optical axis Cof the imaging portionin the optical inspection apparatusaccording to the second embodiment and an illumination openingin a plane orthogonal to an illumination optical axis Cof the illumination portion.

5 FIG. 12 12 24 As illustrated in, the imaging portionaccording to the present embodiment has the same basic structure as that of the imaging portiondescribed in the first embodiment. Each pixel of an image sensorcan receive light of a first wavelength and convert the light into a signal.

14 6 FIG. The illumination portionillustrated inemits illumination light including telecentric illumination.

6 7 FIGS.and 58 58 58 58 58 58 58 58 58 58 58 58 a b c a b c a b b c As illustrated in, in the present embodiment, the illumination openingis defined as a space region including a first light emission region, a second light emission region, and a third light emission region. That is, the illumination openinghas the first light emission region, the second light emission region, and the third light emission region. In the present embodiment, the shapes of the first light emission regionand the second light emission regionare defined by boundaries of concentric circles. Therefore, the second light emission regionand the third light emission regionare considered to be the same light emission region in the present embodiment.

14 1 14 52 54 56 52 6 FIG. The illumination portionmay be any member that can emit illumination light including telecentric illumination formed by the first light flux IL. As an example for realizing telecentric illumination, the illumination portionof the present embodiment includes a projector, a light diffusion portion, and an image forming optical elementfor illumination as illustrated in. In the present embodiment, the projectoris a DLP type projector in which an LED that emits light having a first wavelength is used as a light source.

14 58 58 52 54 54 14 54 56 58 56 1 1 1 2 58 56 2 2 1 2 a b a b The illumination portionforms the first light emission regionand the second light emission regionon an illumination focal plane by the projector. The light diffusion portionis disposed on the illumination focal plane, but the light diffusion portionis not necessarily required. However, in a case where the illumination portionincludes the light diffusion portion, light reaches the entire surface or a wider range of the image forming optical elementfor illumination, and there is an advantage that illuminance unevenness or the like of the illumination light can be uniformized. The light passing through the first light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, the first light flux ILor the first incident light flux ILis formed at a first object point Pand a second object point P. The light passing through the second light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, a second light flux ILor a second incident light flux ILis formed at the first object point Pand the second object point P.

56 58 58 58 58 2 2 2 58 58 2 a b a b b b As described above, an illumination Fourier plane of the image forming optical elementfor illumination has the first light emission regionand the second light emission regiondifferent from the first light emission region. The second light emission regiondoes not include the illumination optical axis C, and forms oblique incidence illumination inclined with respect to the illumination optical axis Cwith the second light flux ILby the light emitted from the second light emission region. The second light emission regionforms oblique illumination with the second light flux ILby emitting light of a first wavelength.

58 58 2 1 2 1 1 2 1 2 58 58 a b a b Light having a first optical property is emitted from the first light emission region, and light having a second optical property is emitted from the second light emission region. In the present embodiment, luminance is considered as the optical property. However, the optical property is not limited thereto, and the optical property may be a wavelength, polarized light, or the like. For example, it is assumed that the luminance as the first optical property is smaller than the luminance as the second optical property. As a result, the total light amount of the second light flux ILcan be made sufficiently larger than the total light amount of the first light flux IL. That is, the second light flux ILcan be made sufficiently brighter than the first light flux IL. However, the the relationship between the total light amounts of the first light flux ILand the second light flux ILis not limited thereto, and the first light flux ILmay be brighter than the second light flux IL. In any case, the optical properties of the light emitted from the first light emission regionand the second light emission regionare different.

58 58 a b It is assumed that both the light from the first light emission regionand the light from the second light emission regioninclude light of the first wavelength.

7 FIG. 58 2 58 54 22 56 26 26 32 34 36 26 32 34 36 38 26 38 58 32 38 26 2 1 58 58 38 26 2 1 a a a a a a a a a b c a a illustrates the illumination openingin a cross section orthogonal to the illumination optical axis C. The illumination openingis assumed to be in the light diffusion portion, for example. Here, the focal length of the image forming optical elementfor imaging is defined as an imaging focal length, the focal length of the image forming optical elementfor illumination is defined as an illumination focal length, and a similar composite openingis obtained by performing similarity transformation on the composite openingin terms of a ratio of the illumination focal length to the imaging focal length. In addition, those corresponding to the first opening region, the second opening region, and the third opening regionof the composite openingare referred to as a first similar opening region, a second similar opening region, and a third similar opening region, respectively. A region corresponding to the shielding regionof the composite openingis referred to as a similar shielding region. In the illumination Fourier plane, the first light emission regionis included in a region where the first similar opening regionand the similar shielding regionare combined, in a case where the similar composite openingis compared on the same plane with the illumination optical axis Caligned with the imaging optical axis C. The second light emission regionand the third light emission regionon the illumination Fourier plane (illumination focal plane) are included in the similar shielding regionin a case where the similar composite openingis compared on the same plane with the illumination optical axis Caligned with the imaging optical axis C.

10 Next, the operation of the optical inspection apparatusaccording to the present embodiment will be described.

14 1 1 2 1 2 1 1 1 1 1 1 11 11 32 26 24 1 a a By the illumination portion, telecentric illumination (telecentric light) formed of the first light flux IL or the incident light flux ILhaving the first wavelength is incident on the first object point Pand the second object point Palong the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, the light flux ILincident on the first object point Pis reflected along the imaging optical axis Caccording to the law of specular reflection. The light (reflected light) of the light flux ILfrom the first object point Pis defined as a first light flux group L. Then, the first light flux group Lpasses through the first similar opening regionof the similar composite openingand forms an image on the image sensor. Thus, the first object point Pconfigures a telecentric image.

14 2 2 1 2 1 2 1 1 2 1 12 12 38 26 12 24 54 26 58 a a a 7 FIG. At the same time, by the illumination portion, obliquely incident light formed from a second light flux ILor an incident light flux ILhaving the first wavelength is incident on the first object point Pand the second object point Pin a direction inclined to the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, light is reflected so that the incident angle and the reflection angle are the same with respect to the imaging optical axis Caccording to the law of specular reflection. The light (reflected light) of the light flux ILfrom the first object point Pis defined as a first-second light beam group L. Then, the first-second light beam group Lreaches the similar shielding regionof the similar composite openingand is shielded. Therefore, the first-second light beam group Lis not imaged on the image sensor. This is because the light diffusion portionand the similar composite openingas the illumination openinghave a relationship illustrated in.

2 1 1 2 21 21 32 34 24 32 34 2 a a a a On the other hand, the second object point Phas the minute defect D, generates scattered light in which the BRDF spreads, and has a component reflected obliquely with respect to the imaging optical axis C. The light (reflected light) of the light flux ILfrom the second object point Pis defined as a second-first light beam group L. The second-first light beam group Lreaches not only the first similar opening regionbut also the second similar opening regionon the imaging Fourier plane (imaging focal plane). Then, an image is formed on the image sensorthrough the similar opening regionsand. As a result, the second object point Pconfigures an entocentric image.

2 2 22 2 21 1 22 2 2 1 2 21 22 21 The light (reflected light) of the light flux ILfrom the second object point Pis defined as a second-second light beam group L. At this time, the reflected light from the second object point Pis mixed with not only a second-first light beam group Lscattered by the first light flux (incident light flux) ILbut also a second-second light beam group Lscattered by the second light flux (incident light flux) IL. The second light flux (incident light flux) ILhas a sufficiently larger light amount than the first light flux (incident light flux) IL. Therefore, the light reflected from the second object point Pin the combination of the second-first light beam group Lwith the second-second light beam group Lhas a sufficiently larger light amount than the light amount of only the second-first light beam group L. That is, there is an effect that the minute defect D is made brighter and sharper.

2 The entocentric image is formed by a light beam group having a numerical aperture NA larger than that of the telecentric image. As described above, the numerical aperture is an important factor for determining the resolution of an optical system, and as the numerical aperture is larger, finer details can be captured. This is because a brighter and clearer image can be acquired as the numerical aperture is simply larger. In particular, in the present embodiment, there is an effect that the minute defect D having a wider BRDF is made sharper by a synergistic effect due to addition of the second light flux (incident light flux) IL.

On the other hand, the magnification of the telecentric image becomes constant even if the position of the object S moves back and forth, and parallax and distortion do not occur. This has an effect of enabling precise dimension measurement of the object S. Further, there is an advantage that an image with uniform resolution can be acquired over the entire imaging field of view. That is, the resolution around the minute defect can always be smaller than the resolution of the minute defect. Therefore, there is an effect that minute defect can be clarified.

10 As described above, there is an effect that the optical inspection apparatusaccording to the present embodiment can sharpen the minute defect D using only the light of the first wavelength.

10 14 Therefore, according to the present embodiment, there are provided the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

8 FIG. 10 Next, a third embodiment will be described with reference to. The present embodiment is a modification of the optical inspection apparatusof the first embodiment and the second embodiment, and the same members as the members described in the first embodiment and the second embodiment or members having the same functions are denoted by the same reference numerals as much as possible, and a detailed description thereof will be omitted.

8 FIG. 12 10 is a schematic cross-sectional view illustrating a relationship between an imaging portionof an optical inspection apparatusand an object S to be inspected according to the present embodiment.

24 12 52 14 1 3 FIG. 6 FIG. Here, in the present embodiment, it is assumed that an image sensorof the imaging portionis a color image sensor, and light of a first wavelength and light of a second wavelength different from the first wavelength can be converted into independent signals in each pixel. Further, a projector(seeor) of the illumination portioncan illuminate a first light flux (incident light flux) ILincluding the light of the first wavelength and the light of the second wavelength.

14 2 1 2 34 The illumination portionemits illumination light including telecentric illumination. The telecentric illumination includes a first wavelength and a second wavelength. The first wavelength is, for example, 375 nm. However, the first wavelength is not limited thereto, and any first wavelength may be used. In the present embodiment, light of the first wavelength is generated by using an ultraviolet LED as a light source. The second wavelength is, for example, 650 nm. However, the second wavelength is not limited thereto, and the second wavelength may be any wavelength. It is assumed that the illumination light has a second light flux ILin a direction different from the first light flux ILforming the telecentric illumination, and the second light flux ILincludes light of a second wavelength. The second opening regionallows light having a first wavelength and light having a second wavelength to pass therethrough.

26 12 32 34 36 32 34 36 34 36 32 34 26 The composite openingof the imaging portionhas a first opening region, a second opening region, and a third opening region. In the present embodiment, the first opening region, the second opening region, and the third opening regionare defined by boundaries of concentric circles. Therefore, the second opening regionand the third opening regionare considered to be the same opening region in the present embodiment. The first opening regionand the second opening regionchange (modify) the properties of the light incident thereon and then pass the light, or pass the light as is without changing (modifying) the properties. Here, the optical properties are a direction, a wavelength, a wavelength spectrum, polarization, luminance, illuminance, and a light flux (light amount) of the incident light flux. In the present embodiment, the composite openingis made of, for example, a glass plate.

32 34 32 34 32 34 32 34 32 The first opening regionand the second opening regionpass light of a first wavelength. However, the first opening regionshields light of the second wavelength. On the other hand, the second opening regionallows not only light of the first wavelength but also light of the second wavelength to pass therethrough. For example, a dielectric multilayer film is applied or deposited on the first opening region, and shields light of the second wavelength. On the other hand, in the second opening region, for example, anti-reflection (AR) that suppresses reflection of light having the first wavelength and further increases transmittance is applied or deposited. However, the first opening regionand the second opening regionare not limited thereto. For example, the first opening regionmay be made of UG-1 glass manufactured by Schott.

26 38 38 32 34 38 34 38 38 38 38 38 2 4 FIGS.and The composite openingmay include a shielding region(see). However, the shielding regionis not necessarily provided. In the present embodiment, the first opening regionand the second opening regionare directly connected. Then, the shielding regionis arranged outside the second opening region. In a case where light of the first wavelength and the second wavelength enters the shielding region, the light is shielded by reflection or absorption. The shielding regionmay be formed on the glass surface by, for example, chromium vapor deposition. However, the present embodiment is not limited thereto, and the shielding regionmay be any member as long as it shields light. The shielding regionmay strongly reflect light, but it is desirable that the reflected light becomes stray light and does not become noise at the time of imaging. Therefore, it is desirable to take measures such as providing an inclination (taper) in the shape of the shielding regionto return the reflected light in a direction in which the reflected light does not become stray light.

32 26 1 32 1 34 1 34 1 32 24 34 24 32 34 32 34 34 24 32 24 The first opening regionin the composite openingintersects with the imaging optical axis C. That is, first opening regionincludes the imaging optical axis C. On the other hand, the second opening regiondoes not intersect with the imaging optical axis C. That is, the second opening regiondoes not include the imaging optical axis C. The light reflected from the object point of the object S and passing through the first opening regionis substantially telecentric light. Then, such light is received by the image sensor, whereby a telecentric image can be acquired. On the other hand, the light reflected from the object point of the object S and passing through the second opening regionbecomes substantially the entocentric light. Then, such light is received by the image sensor, whereby an entocentric image can be acquired. The entocentric light may include light that has passed through the first opening regionas well as the second opening region. That is, the entocentric image can be acquired by the light passing through the first opening regionand the second opening region. However, in order to acquire an entocentric image, it is always necessary to acquire a light reception signal including light passing through the second opening regionby the image sensor. On the other hand, in order to acquire a telecentric image, it is always necessary to acquire a light reception signal of only light passing through the first opening regionby the image sensor.

14 1 The illumination portionemits telecentric illumination formed by the first light flux ILincluding the first wavelength and the second wavelength.

In the present embodiment, the optical property is a wavelength. The first optical property has a first wavelength, and the second optical property has a second wavelength.

10 Next, the operation of the optical inspection apparatusaccording to the present embodiment will be described.

1 1 2 It is assumed that a surface of the object S has a smooth surface orthogonal to the imaging optical axis C. This is defined as an object surface. The first object point Pis a plane. However, it is assumed that a minute defect D exists at the second object point P. The minute defect is irregularities in which a height difference fluctuates, and a height difference is typically tens of micrometers or less. However, the minute defect is not limited to this, and may be any defect as long as the height difference fluctuates.

1 1 24 22 12 2 2 24 1 1 2 The first object point Pis imaged on the first image point Ion the image sensorby the image forming optical elementfor imaging of the imaging portion. Similarly, the second object point Pis imaged on a second image point Ion the image sensor. Since the first object point Pis on a plane, light incident on the first object point Pis reflected such that an incident angle and a reflection angle are equal according to the law of specular reflection. Since the minute defect D exists at the second object point P, the light incident thereon is scattered and reflected in various directions as scattered light. In a case where this scattering angle distribution, that is, information on BRDF is obtained, information on minute irregularities on the object surface can be obtained. For example, the scattering angle distribution in which light is specularly reflected on a flat object surface is narrowed. On the other hand, if minute irregularities are present on the object surface, the scattering angle distribution is generally wide.

14 1 1 2 1 2 1 1 11 12 11 1 12 1 11 12 11 32 26 24 1 11 12 12 32 12 1 24 By the illumination portion, telecentric illumination (telecentric light) formed of a first light flux (or incident light flux) ILhaving a first wavelength and a second wavelength is incident on the first object point Pand the second object point Palong the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, the light is reflected along the imaging optical axis Caccording to the law of specular reflection. This is referred to as first light beam groups Land L. Lis a light beam group of the first wavelength from the first object point P, and Lis a light beam group of the second wavelength from the first object point P. Among the first light beam groups Land L, the first light beam group Lhaving the first optical property (first wavelength) passes through the first opening regionof the composite openingand forms an image on the image sensor. Thus, the first object point Pconfigures a telecentric image. At the same time, among the first light beam groups Land L, the first light beam group Lhaving the second optical property (second wavelength) is shielded by the first opening region. Therefore, the first light beam group Lhaving the second optical property, which is a light beam group obtained by reflecting the first light flux (or incident light flux) ILhaving the second optical property, is not imaged on the image sensor.

2 1 21 22 21 2 22 2 21 22 32 34 21 32 34 22 34 22 32 24 21 22 26 2 On the other hand, the second object point Phas the minute defect D, generates scattered light in which the BRDF spreads, and has a component reflected obliquely with respect to the imaging optical axis C. This is referred to as second light beam groups Land L. Lis a light beam group of the first wavelength from the second object point P, and Lis a light beam group of the second wavelength from the second object point P. The second light beam groups Land Lreach not only the first opening regionbut also the second opening regionon the imaging Fourier plane (imaging focal plane). Then, the second light beam group Lhaving the first optical property passes through the first opening regionand the second opening region, and the second light beam group Lhaving the second optical property passes through the second opening region. On the other hand, the second light beam group Lhaving the second optical property is shielded by the first opening region. Then, an image is formed on the image sensorby the light beam groups Land Lpassing through the composite opening. As a result, the second object point Pconfigures an entocentric image.

21 22 2 2 21 22 1 11 At this time, in the second light beam groups Land L, not only the light having the first optical property but also the light in which the second light flux (incident light flux) ILhaving the second optical property is scattered on the object surface is mixed. That is, at the second image point I, both the light fluxes Land Lhaving the first optical property and the second optical property are received. On the other hand, at the first image point I, only the light Lhaving the first optical property is received. Therefore, the minute defect D is imaged with light having more wavelengths than that of a flat surface. This means that the image of the minute defect D is formed with a light amount larger than the light amount around the minute defect D. Furthermore, it means that the image is imaged with light of more wavelengths, that is, light of multiple colors. As a result, there is an effect that the minute defect D is brightened and sharpened, and is easily identified by color change or the number of colors.

The entocentric image is formed by a light beam group having a numerical aperture NA larger than that of the telecentric image. The numerical aperture is an important factor for determining the resolution of the optical system, and as the numerical aperture is larger, finer details can be captured. This is because a brighter and clearer image can be acquired as the numerical aperture is simply larger. In particular, in the present embodiment, there is an effect that the minute defect in which the BRDF becomes wider is more sharpened synergistically by adding the second light flux (incident light flux).

On the other hand, in the telecentric image, the magnification becomes constant even if the position of the object moves back and forth, and parallax and distortion do not occur. This has an effect of enabling precise dimension measurement of the object. Further, there is an advantage that an image with uniform resolution can be acquired over the entire imaging field of view. That is, the resolution around the minute defect can always be smaller than the resolution of the minute defect. Therefore, there is an effect that minute defect can be clarified.

10 As described above, there is an effect that the optical inspection apparatusaccording to the present embodiment can sharpen minute defects using two wavelengths.

10 14 Therefore, according to the present embodiment, there are provided the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

9 11 FIGS.to A fourth embodiment will be described with reference to. The present embodiment is a modification of the third embodiment, and a difference will be described.

9 FIG. 10 FIG. 11 FIG. 12 10 26 1 12 10 26 1 12 10 58 2 14 is a schematic cross-sectional view illustrating a relationship between an object S to be inspected and an imaging portionof an optical inspection apparatusaccording to the fourth embodiment.is a schematic view illustrating composite openingin a plane orthogonal to an imaging optical axis Cof the imaging portionof the optical inspection apparatusaccording to the fourth embodiment.is a schematic view illustrating the composite openingin a plane orthogonal to the imaging optical axis Cof the imaging portionof the optical inspection apparatusaccording to the fourth embodiment and an illumination openingin a plane orthogonal to an illumination optical axis Cof an illumination portion.

Here, the first wavelength is 450 nm, and the second wavelength is 650 nm. An optical property is a wavelength, a first optical property is a first wavelength, and a second optical property is a second wavelength.

9 10 FIGS.and 26 34 36 32 34 32 34 26 32 34 As illustrated in, the composite openingof the present embodiment is concentric. Therefore, a second opening regionand a third opening regioncan be regarded as the same. The first opening regionis directly connected to the second opening region. In addition, the first opening regionallows not only the light having the first wavelength but also the light having the second wavelength to pass therethrough. The second opening regionallows light having the second wavelength to pass, but shields light having the first wavelength. In order to form such a composite opening, for example, a through hole may be provided at the center portion of a colored glass that transmits the light having the second wavelength and absorbs the light having the first wavelength, the through hole may be used as the first opening region, and the periphery thereof may be used as the second opening region.

26 38 34 38 The composite openingincludes a shielding regionaround the second opening region. The shielding regionshields light of the first wavelength and light of the second wavelength.

22 26 26 32 34 36 32 34 36 38 38 a a a a a. 11 FIG. 10 FIG. A focal length of the image forming optical elementfor imaging is defined as an imaging focal length, a focal length of the image forming optical element for illumination is defined as an illumination focal length, and a similar composite openingillustrated inis obtained by performing similar transformation on the composite openingillustrated inin terms of a ratio of the illumination focal length to the imaging focal length. Furthermore, those corresponding to the first opening regionand the second opening region(third opening region) are referred to as a first similar opening regionand a second similar opening region(third similar opening region), respectively. A region corresponding to the shielding regionis a similar shielding region

11 FIG. 58 58 58 58 58 58 58 58 1 58 2 a b c b c a b As illustrated in, the illumination openingincludes a first light emission region, a second light emission region, and a third light emission region. The illumination openingis concentric. Therefore, the second light emission regionand the third light emission regioncan be regarded as the same. Light of the first wavelength is emitted from the first light emission regionto form a first light flux (incident light flux) ILhaving a first optical property (first wavelength). Light of the second wavelength is emitted from the second light emission regionto form a second light flux (incident light flux) ILhaving a second optical property (second wavelength).

58 58 38 26 2 1 b c a a The second light emission regionand the third light emission regionon the illumination Fourier plane (illumination focal plane) are included in the similar shielding regionin a case where the similar composite openingis compared on the same plane with the illumination optical axis Caligned with the imaging optical axis C.

10 Next, the operation of the optical inspection apparatusaccording to the present embodiment will be described.

14 1 2 The illumination portionilluminates the object S with the first light flux (incident light flux) ILand the second light flux (incident light flux) IL.

58 56 1 1 1 2 58 56 2 2 1 2 a b The light of the first wavelength having passed through the first light emission regionilluminates the surface of the object S by an image forming optical elementfor illumination. Here, the first light flux ILor the first incident light flux ILis formed at a first object point Pand a second object point P. The light of the second wavelength having passed through the second light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, a second light flux ILor a second incident light flux ILis formed at the first object point Pand the second object point P.

14 1 1 2 1 2 1 1 11 11 32 26 24 1 By the illumination portion, telecentric illumination (telecentric light) formed of a first light flux (or incident light flux) ILhaving a first wavelength is incident on the first object point Pand the second object point Palong the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, the light is reflected along the imaging optical axis Caccording to the law of specular reflection. This is referred to as a first-first light flux group L. The first-first light flux group Lhaving the first optical property (first wavelength) passes through the first opening regionof the composite openingand is imaged on the image sensor. Thus, the first object point Pconfigures a telecentric image.

14 2 2 1 2 1 2 1 1 12 12 38 26 12 24 54 26 58 11 FIG. At the same time, by the illumination portion, obliquely incident light formed from the second light flux ILor the incident light flux ILhaving the second wavelength is incident on the first object point Pand the second object point Pin a direction inclined to the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, light is reflected so that the incident angle and the reflection angle are the same with respect to the imaging optical axis Caccording to the law of specular reflection. This is referred to as a first-second light flux group L. Then, the first-second light flux group Lreaches the shielding regionof the composite openingand is shielded. Therefore, the first-second light flux group Lis not imaged on the image sensor. This is because the light diffusion portionand the composite openingas the illumination openinghave a relationship illustrated in.

2 1 21 22 2 32 34 34 21 22 2 24 32 34 On the other hand, the second object point Phas the minute defect D, generates scattered light in which the BRDF spreads, and has a component reflected obliquely with respect to the imaging optical axis C. A second-first light flux group Lof the first wavelength and a second-second light flux group Lof the second wavelength from the second object point Preach not only the first opening regionbut also the second opening region. However, the second opening regionshields second-first light flux group Lof the first wavelength and passes the second-second light flux group Lof the second wavelength. As a result, the second object point Pconfigures an entocentric image. Then, an image is formed on the image sensorthrough the opening regionsand.

2 22 2 58 2 58 58 2 1 2 22 10 a b a At this time, the reflected light from the second object point Pincludes a second-second light flux group L. Therefore, the reflected light from the second object point Pincludes light of the second wavelength. The first light emission regionhas, for example, a small circular shape including the illumination optical axis C, and the second light emission regioncan have a sufficiently larger area than the first light emission region. Therefore, the light amount of the second light flux ILhaving the second optical property (second wavelength) can be sufficiently larger than the light amount of the first light flux IL. As a result, the minute defect D scatters the second light flux (incident light flux) ILhaving a large light amount, and generates the second-second light flux group Lhaving a large light amount. Therefore, the optical inspection apparatusaccording to the present embodiment has an effect of brightening and sharpening the minute defect D.

10 14 Therefore, according to the present embodiment, there are provided the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

12 13 FIGS.and 5 7 FIGS.to 8 FIG. A fifth embodiment will be described with reference to. The present embodiment is basically a modification of the second embodiment (see) and the third embodiment (see), and a difference will be described.

12 FIG. 13 FIG. 12 10 26 1 12 10 58 2 14 is a schematic cross-sectional view illustrating a relationship between an object S to be inspected and an imaging portionof an optical inspection apparatus.is a schematic view illustrating a composite openingin a plane orthogonal to an imaging optical axis Cof the imaging portionof the optical inspection apparatusaccording to the present embodiment and an illumination openingin a plane orthogonal to an illumination optical axis Cof an illumination portion.

24 12 In addition to a first wavelength, illumination light includes light having a second wavelength different from the light having the first wavelength, and light having a third wavelength different from the light having the first wavelength and the light having the second wavelength. The first wavelength is 450 nm, the second wavelength is 750 nm, and the third wavelength is 550 nm. These are blue light, red light, and green light. The image sensorof the imaging portioncan convert the light of these wavelengths into independent signals in each pixel.

13 FIG. 58 58 58 58 58 58 58 58 58 a b c a b c b c In the present embodiment, as illustrated in, an illumination openinghas a first light emission region, a second light emission region, and a third light emission region. In the present embodiment, the shapes of the first light emission region, the second light emission region, and the third light emission regionare defined by boundaries of concentric circles. Therefore, the second light emission regionand the third light emission regionare considered as separate light emission regions in the present embodiment.

56 58 58 58 58 58 2 c a b b c As described above, it is assumed that an illumination Fourier plane of an image forming optical elementfor illumination has the third light emission regiondifferent from the first light emission regionand the second light emission region, and the second light emission regionand the third light emission regiondo not include the illumination optical axis C.

14 58 58 58 52 54 54 14 54 56 a b c The illumination portionforms the first light emission region, the second light emission region, and the third light emission regionon an illumination focal plane by, for example, a projector. The light diffusion portionis disposed on the illumination focal plane, but the light diffusion portionis not necessarily required. However, in a case where the illumination portionincludes the light diffusion portion, light reaches the entire surface or a wider range of the image forming optical elementfor illumination, and there is an advantage that illuminance unevenness or the like of the illumination light can be uniformized.

58 58 58 58 58 52 58 52 58 52 a b c a b c In this manner, light having the first optical properties is emitted from the first light emission regionof the illumination opening, light having the second optical properties is emitted from the second light emission region, and light having the third optical properties is emitted from the third light emission region. The optical property is a wavelength, the first optical property is a first wavelength, the second optical property is a second wavelength, and the third optical property is a third wavelength. Therefore, the first light emission regionallows the light having the first wavelength among the light including the first wavelength, the second wavelength, and the third wavelength from the projectorto pass therethrough, but shields the light having the second wavelength and the third wavelength. The second light emission regionallows the light having the second wavelength among the light including the first wavelength, the second wavelength, and the third wavelength from the projectorto pass therethrough, but shields the light having the first wavelength and the third wavelength. The third light emission regionallows light of a third wavelength among light including the first wavelength, the second wavelength, and the third wavelength from the projectorto pass therethrough, but shields light of the first wavelength and the second wavelength.

58 1 58 58 a b c The first light emission regionforms substantially parallel illumination (telecentric illumination) along the imaging optical axis Cwith a first light flux by emitting light of a first wavelength. The second light emission regionforms oblique illumination with a second light flux by emitting light of a second wavelength. The third light emission regionforms oblique illumination with a third light flux by emitting light of a third wavelength.

26 34 36 32 34 36 The composite openingin the present embodiment is concentric. Therefore, a second opening regionand a third opening regioncan be regarded as the same. The first opening region, the second opening region, and the third opening regionallow light of a first wavelength, a second wavelength, and a third wavelength to pass therethrough.

26 26 32 34 36 26 32 34 36 38 26 38 58 32 26 2 1 58 58 38 26 2 1 a a a a a a a a b c a a It is assumed that the composite openingaccording to the present embodiment is a similar composite opening. Those corresponding to the first opening region, the second opening region, and the third opening regionof the composite openingare referred to as a first similar opening region, a second similar opening region, and a third similar opening region, respectively. A region corresponding to the shielding regionof the composite openingis referred to as a similar shielding region. The first light emission regionin the illumination Fourier plane is included in the first similar opening regionin a case where the similar composite openingis compared on the same plane with the illumination optical axis Caligned with the imaging optical axis C. The second light emission regionand the third light emission regionon the illumination Fourier plane (illumination focal plane) are included in the similar shielding regionin a case where the similar composite openingis compared on the same plane with the illumination optical axis Caligned with the imaging optical axis C.

26 38 38 32 34 2 4 FIGS.and The composite openingmay include a shielding region(see). However, the shielding regionis not necessarily provided. In the present embodiment, the first opening regionand the second opening regionare directly connected.

10 Next, the operation of the optical inspection apparatusaccording to the present embodiment will be described.

14 1 2 3 1 2 The illumination portionilluminates the object S with a first light flux (incident light flux) IL, a second light flux (incident light flux) IL, and a third light flux (incident light flux) ILdifferent from the first light flux ILand the second light flux IL.

58 56 1 1 1 2 58 56 2 2 1 2 58 56 3 3 1 2 a b c The light of the first wavelength having passed through the first light emission regionilluminates the surface of the object S by an image forming optical elementfor illumination. Here, the first light flux ILor the first incident light flux ILis formed at a first object point Pand a second object point P. The light of the second wavelength having passed through the second light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, a second light flux ILor a second incident light flux ILis formed at the first object point Pand the second object point P. The light of the third wavelength having passed through the third light emission regionilluminates the surface of the object S by the image forming optical elementfor illumination. Here, the third light flux ILor the third incident light flux ILis formed at the first object point Pand the second object point P.

14 1 1 2 1 2 1 1 11 11 32 26 24 1 By the illumination portion, telecentric illumination (telecentric light) formed of a first light flux (or incident light flux) ILhaving a first wavelength is incident on the first object point Pand the second object point Palong the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, the light is reflected along the imaging optical axis Caccording to the law of specular reflection. This is referred to as a first-first light flux group L. The first-first light flux group Lhaving the first optical property (first wavelength) passes through the first opening regionof the composite openingand is imaged on the image sensor. Thus, the first object point Pconfigures a telecentric image.

14 2 2 1 2 1 2 1 1 12 12 38 26 12 24 54 26 58 a 13 FIG. At the same time, by the illumination portion, obliquely incident light formed from the second light flux ILor the incident light flux ILhaving the second wavelength is incident on the first object point Pand the second object point Pin a direction inclined to the imaging optical axis Cor the illumination optical axis C. Since the first object point Pis a plane, light is reflected so that the incident angle and the reflection angle are the same with respect to the imaging optical axis Caccording to the law of specular reflection. This is referred to as a first-second light flux group L. Then, the first-second light flux group Lreaches the similar shielding regionof the composite openingand is shielded. Therefore, the first-second light flux group Lis not imaged on the image sensor. This is because the light diffusion portionand the similar composite openingas the illumination openinghave a relationship illustrated in.

14 3 3 1 2 1 2 3 1 2 2 1 1 13 13 38 26 13 24 3 1 12 3 22 12 3 54 26 58 3 12 a 13 FIG. At the same time, by the illumination portion, obliquely incident light formed from the third light flux ILor the incident light flux ILhaving the third wavelength is incident on the first object point Pand the second object point Pin a direction inclined to the imaging optical axis Cor the illumination optical axis C. The third light flux ILis inclined to the imaging optical axis Cor the illumination optical axis Cmore than the second light flux IL. Since the first object point Pis a plane, light is reflected so that the incident angle and the reflection angle are the same with respect to the imaging optical axis Caccording to the law of specular reflection. This is referred to as a first-third light beam group L. Then, the first-third light beam group Lreaches the shielding regionof the composite openingand is shielded. Therefore, the first-third light beam group Lis not imaged on the image sensor. Therefore, in a case where the third light flux ILis reflected by the first object point Pon the plane of the object S, the reflected light does not reach the imaging portion. That is, the light flux ILhaving the third optical property does not reach the image forming optical elementfor imaging of the imaging portioneven if the light flux ILis reflected by the plane of the object S. This is because the light diffusion portionand the similar composite openingas the illumination openinghave a relationship illustrated in. At this time, there is an effect that stray light due to the third light flux ILis not generated in the imaging portion.

2 1 21 22 23 2 32 34 2 24 32 34 2 21 22 23 2 2 1 11 On the other hand, the second object point Phas the minute defect D, generates scattered light in which the BRDF spreads, and has a component reflected obliquely with respect to the imaging optical axis C. The second-first light flux group Lhaving the first wavelength, the second-second light flux group Lhaving the second wavelength, and the second-third light flux group Lhaving the third wavelength from the second object point Preach not only the first opening regionbut also the second opening region. As a result, the second object point Pconfigures an entocentric image. Then, an image is formed on the image sensorthrough the opening regionsand. At this time, the reflected light from the second object point Pincludes a second-first light beam group L, a second-second light beam group L, and a second-third light beam group L. Therefore, the reflected light from the second object point Pincludes the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength. Therefore, the reflected light from the second object point Pcan obtain a large pixel value as compared with the case of including only the light of the first wavelength like the reflected light from the first object point P(the first-first light beam group L). That is, there is an effect that the minute defect D is made brighter and sharper.

3 10 In addition, the light amount of the third light flux ILcan be sufficiently large. Therefore, the optical inspection apparatusaccording to the present embodiment has an effect of brightening and sharpening the minute defect D.

10 In addition, the optical inspection apparatusaccording to the present embodiment has an effect that it is possible to acquire BRDF information of the minute defect D and to acquire more detailed information on the minute defect D by analyzing the relative intensity of the pixel value with respect to each of blue light, red light, and green light from the image of the minute defect D.

10 14 Therefore, according to the present embodiment, there are provided the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

10 14 According to at least one embodiment described above, it is possible to provide the optical inspection apparatusand the optical inspection method capable of inspecting the fine structure (minute defect) of the object surface without dispersing the light from the illumination portion (light source).

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.